Polycocondensates based on aspartic acid, their preparation and their use

ABSTRACT

Polycocondensates based on aspartic acid which are obtainable by condensing aspartic acid in the presence of polymers containing carboxyl groups, which contain at least 10 mol % of a monoethylenically unsaturated carboxylic acid in copolymerized form and have a molecular weight of at least 300, in the weight ratio from 1,000:1 to 2:1, processes for preparing the polycocondensates and use of the polycocondensates in the form of the free acid groups or in a form neutralized with ammonia, amines, alkali metal or alkaline earth metal bases as an additive to detergents and cleaners, as scale inhibitors or as dispersants for finely divided solids are described.

The invention relates to polycocondensates based on aspartic acid, whichare obtainable by condensing aspartic acid in the presence of polymerscontaining carboxyl groups, processes for preparing thepolycocondensates and the use of the polycocondensates as an additive todetergents and cleaners, as scale inhibitors or as dispersants forfinely divided solids.

U.S. Pat. No. 3,634,543 discloses grafting copolymers of olefins having2 to 4 carbon atoms, containing from 1 to 50 mol % of acrylic acid ormethacrylic acid, with caprolactam.

WO-A-92/11297 discloses reacting copolymers of α-olefins andmonoethylenically unsaturated carboxylic acids having molecular weightsfrom 500 to 6,000 with ω-aminocarboxylic acids. The reaction productshave an excellent compatibility with other polymers, in particular withpolyamides.

EP-A-0 452 696 discloses aqueous solutions or dispersions ofhydroxy-functional copolymers containing imide structural units, whichare prepared, for example, by reacting copolymers containing anhydridegroups or, if appropriate, carboxyl groups with aminoalcohols with imideformation at temperatures from 100° to 200° C., removing the water ofreaction by azeotropic distillation and dissolving the polymer solutionin water or dispersing it after at least partial neutralization of thecarboxyl groups and, if appropriate, partially or completely removingorganic solvent which is still present by azeotropic distillation. Thehydroxy-functional copolymers are used for the preparation of coatingcompositions, sealing compositions or adhesives.

It is an object of the present invention to make available novelsubstances. A further object of the invention is to indicate noveladditives for use in detergents and clenaers and to make available novelscale inhibitors and dispersants.

We have now found that these objects are achieved by polycondensatesbased on aspartic acid, which are obtainable by condensing (a) asparticacid or polyaspartic acid in the presence of (b) polymers containingcarboxyl groups, which contain at least 10 mol % of a monoethylenicallyunsaturated carboxylic acid in copolymerized form and have a molecularweight of at least 300, or of copolymers containing maleic anhydridegroups in the weight ratio (a):(b) from 1,000:1 to 2:1.

The object is additionally achieved by a process for preparingpolycondensates based on aspartic acid when (a) aspartic acid orpolyaspartic acid is condensed in the presence of (b) polymerscontaining carboxyl groups, which contain at least 10 mol % of amonoethylenically unsaturated carboxylic acid in copolymerized form andhave a molecular weight of at least 300, or of copolymers containingmaleic anhydride groups in the weight ratio (a) to (b) from 1,000:1 to2:1.

The last-mentioned objects are achieved by the use of thepolycocondensates in the form of the free acid groups or in a formneutralized with ammonia, amines, alkali metal or alkaline earth-metalbases as an additive to detergents and cleaners, as scale inhibitors oras dispersants for finely divided solids.

Components (a) which can be used for preparing the polycocondensates areL-, D- and DL-aspartic acid. DL-Aspartic acid is easily accessibleindustrially, eg. by reaction of ammonia with maleic acid or fumaricacid. L-Aspartic acid is obtainable, for example, by asymmetricL-aspartase-catalyzed addition of ammonia to fumaric acid. Preferably,L- and DL-aspartic acid or mixtures of these isomers are used forpreparing the polycocondensates.

Suitable components (b) are polymers containing carboxyl groups, whichcontain at least 10 mol % of a monoethylenically unsaturated carboxylicacid in copolymerized form and have a molecular weight of at least 300.These polymers can be homopolymers of monoethylenically unsaturatedcarboxylic acids or copolymers of these carboxylic acids with othermonoethylenically unsaturated monomers copolymerizable therewith orcopolymers of at least 2 monoethylenically unsaturated carboxylic acidsor anhydrides. Suitable monoethylenically unsaturated carboxylic acidspreferably contain 3 to 8 carbon atoms in the molecule, eg. acrylicacid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid,crotonic acid, citraconic acid, aconitic acid, methylenemalonic acid,methylenesuccinic acid, ethylacrylic acid and itaconicic acid. Preferredpolymers containing carboxyl groups are, for example, homopolymers ofmaleic acid, acrylic acid and methacrylic acid and also copolymers ofacrylic acid and methacrylic acid in any desired ratio and copolymers ofacrylic acid and maleic acid, eg. in the molar ratio from 10:90 to90:10. The molecular weight of the homo- and copolymers which areemployed as component (b) is from 300 to 250,000 and is preferably inthe range from 350 to 100,000. The homo- and copolymers of themonoethylencially unsaturated carboxylic acids can be prepared accordingto all known processes by polymerizing the monomers in aqueous medium orin an organic solvent in the presence of radical-forming initiators. Inprinciple, all known processes for substance, solution, emulsion andprecipitation polymerization are suitable for preparing the polymers.Preferably, polymers prepared by solution polymerization processes inwater at temperatures from 50° to 180° C. in the presence ofradical-forming initiators or polymers prepared by substancepolymerization at from 180° to 350° C. are employed as component (b).Thus, for example, copolymers of acrylic acid and maleic anhydridehaving molecular weights from 300 to 30,000 are obtained by addingacrylic acid and maleic anhydride continuously to a high-temperaturereactor at from 200° to 350° C. and polymerizing therein. Thepolymerization can in this case be carried out in the absence oralternatively in the presence of initiators which form radicals underthe polymerization conditions. As a result of the effect of water on thecopolymers, the anhydride groups hydrolyze to free carboxyl groups.

Copolymers of acrylic acid and methacrylic acid are preferably preparedby solution polymerization in water according to the process known fromEP-B-0 075 820 or alternatively by polymerizing in organic solvents inthe presence of radical polymerization initiators.

Dimerized or oligomerized unsaturated fatty acids can also be used,which are obtainable, for example, by cycloaddition of mono- orpolyunsaturated fatty acids.

If desired, the monoethylenically unsaturated carboxylic acids can becopolymerized in the presence of other monoethylenically unsaturatedmonomers which are copolymerizable therewith. The other monomers whichare copolymerized with the monoethylenically unsaturated carboxylicacids are, if they are additionally used in the copolymerization,contained in copolymerized form in amounts from 5 to 95, preferably 10to 90% by weight. The copolymers should contain at least 10 mol % of theethylenically unsaturated carboxylic acids in copolymerized form.Suitable other monomers which are copolymerizable with themonoethylenically unsaturated carboxylic acids are, for example, vinylethers, vinyl esters, alkyl acrylates, alkyl methacrylates, styrene,N-vinylpyrrolidone, acrylamide, methacrylamide, acrylonitrile,methacrylonitrile, allyl alcohol and allyl alcohol ethoxylates, furansand olefins having 2 to 30 C atoms. Other suitable monomers arepolyalkylene glycol monovinyl ethers, polyethylene glycol C₁ -C₂₂-alkylvinyl ethers, N-vinylformamide and N-vinylacetamide. Copolymerswhich contain vinyl esters, N-vinylformamide or N-vinylacetamide incopolymerized form can be converted by hydrolysis into polymerscontaining vinyl alcohol and vinylamine units. Examples of suitablecopolymers of monoethylenically unsaturated carboxylic acids or theiranhydrides with other monoethylenically unsaturated compounds are:

copolymers of vinyl acetate and maleic acid,

copolymers of vinyl acetate and acrylic acid or methacrylic acid,

terpolymers of vinyl acetate, maleic acid and acrylic acid ormethacrylic acid,

polymers of vinyl acetate, acrylic acid and/or maleic acid, the vinylacetate units being contained in partially or completely hydrolyzed formas vinyl alcohol units,

copolymers of methacrylic acid and methyl methacrylate,

copolymers of butyl acrylate and acrylic acid,

copolymers of styrene and maleic anhydride,

polyoleic acid,

polylauric acid,

graft polymers of acrylic acid and/or maleic acid to polyethyleneglycols and/or polypropylene glycols,

polycondensates of terephthalic acid and polyalkylene oxides with acidend groups,

copolymers of vinylsulfonic acid and maleic acid,

terpolymers of isobutene, maleic acid and acrylic acid,

copolymers of acrylamide and acrylic acid,

copolymers of acrylamide and maleic anhydride,

terpolymers of acrylamide with arylic acid and maleic anhydride,

copolymers of N-vinylpyrrolidone and maleic acid and/or acrylic acid,

copolymers of N-vinylformamide and maleic anhydride,

copolymers of N-vinylformamide and acrylic acid,

terpolymers of N-vinylformamide and acrylic acid and maleic acid,

copolymers of vinylamine and acrylic acid,

copolymers of vinylamine and maleic acid,

terpolymers of vinylamine, acrylic acid and maleic acid,

terpolymers of diisobutene, maleic acid and acrylic acid,

copolymers of isobutylene and maleic anhydride,

copolymers of octadecene and maleic anhydride,

polyethylene waxes grafted with maleic anhydride,

copolymers of vinylphosphonic acid and maleic acid,

copolymers of methyl vinyl ethers with maleic anhydride,

copolymers of 1,4-butanediol monovinyl ether ethoxylates

diethyl maleate and/or acrylic acid and/or butyl acrylate and alsocopolymers of diethylene glycol ethyl vinyl ether, maleic anhydrideand/or acrylic acid.

The copolymers containing maleic anhydride in copolymerized form can bepartially hydrolyzed prior to the reaction with aspartic acid so thatthe copolymers contain, for example, 10 mol % of maleic acid units. Themolecular weight of the copolymers specified above is from 300 to250,000. The homo- and copolymers described above exhibit a molecularweight distribution. The measurement specified for the distribution iscustomarily the ratio M_(w) /M_(n), whose numerical value for thesehomo- and copolymers is greater than 1 and customarily in the range from1.01 to 50.

The polycocondensates based on aspartic acid are prepared, for example,by subjecting aspartic acid and the polymers (b) jointly topolycondensation or by first polycondensing aspartic acid to givepolyaspartic acid or polyaspartimide and, after addition of the polymer(b), carrying out the polycocondensation. All polycondensationtechniques can be used for this purpose. Examples are solution, solidphase or melt polycondensation. In a preferred embodiment for preparingthe polycocondensates according to the invention, the components (a) and(b) are employed for polycocondensation in a solution in phosphoricacid. In this procedure, condensation can be carried out in theapparatuses equipped with a stirrer which are customarily present inmanufacturing plants. In the case of polycocondensation with the polymer(b), the ratio of aspartic acid to phosphoric acid can be from 1:0.1 to1:10 and is preferably in the range from 1:1 to 1:5.

The polycocondensation of the components (a) and (b) is carried out atfrom 80° to 270°, preferably 120° to 250° C.

A further preparation variant consists in making a suspension orsolution of the carboxyl-carrying polymer (b) and aspartic acid inwater, then evaporating the water and polycocondensing the residuethermally at up to 270° C.

An elegant procedure consists in polymerizing acrylic acid and/ormethacrylic acid and/or maleic acid in phosphoric acid or phosphoricacid/water mixtures by means of radicals and, treating the resultingphosphoric acid reaction solution with aspartic acid or polyasparticacid and polycocondensing with removal of water.

Besides carboxyl groups, suitable copolymers (b) can also containderivatives of carboxylic acids, eg. in the form of the salts, theesters, the amides, the anhydrides or the nitriles. The carboxylic acidgroups of the polymers (b) react with aspartic acid. Reaction productsare preferred in which 5 to 95% of the carboxylic acid groups of thepolymer (b) are involved in the linkage and in which the remainingcarboxylic acid groups are present either in the acid form, as ananhydride or in the form of the salt. The polycocondensates can containstructural elements in which polyaspartic acids or polyaspartimideswhich consist of at least 2 aspartic acid units are bonded in salt-like,imide-like or amide-like form to at least one or more of the carboxylicacid groups contained in the polymer (b). For example, in thepolycocondensation of aspartic acid with polymers containing maleicanhydride groups the structure I or IV is formed and in thepolycocondensation of aspartic acid with acrylic acid polymers thestructures II and III can be formed: ##STR1##

In the structures I to IV specified above, m is the proportion of thecarboxylic acids in the polymer (b) which is linked to aspartic acid andn is the number of aspartic acid or aspartimide units which are graftedto the polymer (b). The components (a) and (b) are reacted in thepolycondensation in a weight ratio from 1,000:1 to 2:1, preferably 100:1to 5:1. In this process, polycocondensates are formed which in 1%strength solution in dimethylformamide have K values according toFikentscher of from 8 to 100, preferably 9 to 60. By hydrolysis of theimide form of the polycocondensates, polyaspartic acids linked in α- andβ-form can be contained in the polycocondensates. The proportion of α-and β-linked aspartic acids can be affected by the hydrolysisconditions, eg. the pH and the temperature during the hydrolysis.

The content of polymer (b) in the polycocondensates can be determinedusing customary spectroscopic methods.

Acrylic acid-containing polycocondensates are preferably studied bymeans of H-NMR spectroscopy. If, for example, a polyacrylic acid havinga molecular weight of 100,000 is polycocondensed with aspartic acid, inthe polycocondensate the presence of polyacrylic acid can be recognizedby signals of the --CH₂ group from 1.0 to 2.0, and of the --CH(COOH)group at 2.5-3.0 in addition to the signals of the polyaspartimidecomponent at 2.5-3.0, 3.0-3.5 and 5.0-5.8.

If copolymers of acrylic acid and maleic acid are used as polymer (b),the copolymerized and cocondensed acrylic acid fractions in thepolycocondensates can be recognized particularly readily by means ofH-NMR spectroscopy. The signals of polymaleic acid are less highlysuited for identification. In these cases, C--NMR spectroscopy is bettersuited for structural elucidation. After the polycocondensation, thepolycocondensates can be converted into the salt form by treatment withbases, eg. sodium hydroxide solution, potassium hydroxide solution,sodium hydrogen carbonate, potassium hydrogen carbonate, sodiumcarbonate, potassium carbonate, calcium hydroxide, barium hydroxide,ammonia or amines such as triethanolamine, monoethanolamine ortrimethylamine. The polycondensates have, for example, K values from 10to 100 (determined according to H. Fikentscher on the sodium salts ofthe polycocondensates in 1% strength aqueous solution at pH 7 and 25°C.).

The aspartic acid component in the polycocondensates is biodegradable inaqueous solution. In the form of poorly soluble salts, thepolycocondensates are compostable and degradable.

The polycocondensates according to the invention are used in the form ofthe imides, the free acids and preferably in the form of the salts withalkali metal or ammonium bases as additives to detergents and cleaners,as scale inhibitors in water treatment or as dispersants for finelydivided solids such as clay minerals, coal, ores, metal oxides, metalsulfides, chalk and titanium dioxide. When used as dispersants, theamounts to be used are from about 0.1 to 5% by weight, based on thefinely divided solid. When used as scale inhibitors, the amounts usedare as a rule from 1 to 100 ppm, based on the water to be treated. Thepolycocondensates to be used according to the invention in particularprevent the formation and the growth of water hardeners, in particularof calcium carbonate, calcium phosphate, barium sulfate, calcium sulfateand magnesium hydroxide.

When used as an additive in phosphate-reduced or phosphate-freedetergents and cleaners, the polycocondensates according to theinvention are employed in amounts from 0.1 to 30, preferably 0.5 to 10%by weight, based on the particular formulations. Phosphate-reduceddetergents are understood as meaning those formulations which containnot more than 25% by weight of phosphate, calculated as sodiumtriphosphate. The composition of the detergent and cleaner formulationscan be very different. They customarily contain from 2 to 50% by weightof surfactants and, if appropriate, builders. These details apply bothto liquid and to powdered detergents and cleaners. Examples of thecomposition of detergent formulations which are customary in Europe, inthe USA and Japan are found, for example, compiled in the form of atable in Chemical and Engineering Use, volume 67 (1989), 35. Thepolycocondensates according to the invention are used in the productionof liquid and powdered detergents as viscosity regulators, becuase theygreatly reduce the viscosity of aqueous surfactant solutions and zeolitesuspensions. During washing, they display encrustation-inhibiting anddispersant action and assist the primary and secondary washing action.

In the detergent liquor, the polycocondensates according to theinvention have a good dispersing power for particulate dirt, inparticular for clay minerals (clay). This property is thereforeimportant, because clay soilings of textile material are wide-spread.The polycocondensates are builders for detergents and during the washingprocess cause a reduction in encrustation and graying on the washedtextile material. They are thus also suitable as encrustation andgraying inhibitors in detergents.

Additionally, those detergent formulations are of interest which containup to 60% by weight of an alkali metal silicate and up to 10% by weightof a polycocondensate according to the invention. Suitable alkali metalsilicates are, for example, the amorphous sodium disilicates which aredescribed in EP-A-0 444 415, and also crystalline layered silicateswhich according to EP-A-0 337 219 are contained in detergentformulations as builders and according to EP-B-0 164 514 are used forsoftening water, and sodium silicates which are obtainable bydehydrating sodium silicate solutions and drying up to water contentsfrom 15 to 23, preferably 18 to 20% by weight.

If appropriate, detergents can additionally contain a bleaching agent,eg. sodium perborate which, if it is used, can be contained in amountsof up to 30% by weight in the detergent formulation. Thepolycocondensates according to the invention can additionally be usedwith other polymers which are customarily employed in detergents. Forthis purpose, the polycocondensates according to the invention can bemixed, for example, with the other polymers, eg. in the weight ratiofrom 1:20 to 20:1, or they can be added separately in the production ofthe detergents. Other suitable polymers are, for example, polyalkyleneglycols, polyacetals, graft polymers of vinyl acetate or methyl acrylateto polyalkylene oxides having molecular weights of up to 100,000, whichmay be terminated by end groups, graft copolymers of acrylic acid ormethacrylic acid and maleic acid to natural substances such as starch,degraded starches, mono- and oligosaccharides, and also copolymers ofacrylic acid and maleic acid having molecular weights from 5,000 to250,000, homopolymers of acrylic acid and methacrylic acid havingmolecular weights up to 200,000 and copolymers of acrylic acid andmethacrylic acid having molecular weights from 2,000 to 200,000 and alsopolymaleic acid having molecular weights from 500 to 50,000. Otherpolymers which are additionally suitable are polyesters containing acidgroups, pectins, pectic acid or carboxymethylcellulose.

The K values of the polycocondensates were determined in 1% strengthsolution in water at pH 7 and 25° C. in the Na salt form according to H.Fikentscher, Cellulose-Chemie [Cellulose Chemistry], volume 13 (1932),58-64 and from 71 to 74. The molecular weights of the polymers b) usedwere determined by means of GPC. The calibration of the GPC analysis wascarried out using polyacrylic acid standards which were calibrated bylight-scattering measurements.

EXAMPLES 1 TO 9

26 g of the polymers specified in the table are initially introducedinto a reactor of 2 l capacity and mixed with 390 g of 75% strengthaqueous phosphoric acid and then treated with 266 g of aspartic acid.The reaction mixture is heated to 100° C. under a pressure of 100 mbar,water being removed from the reaction mixture by distillation. Thereaction mixture is then heated to 160° C. under a pressure of 50 mbarfor 2 h, the polycocondensation being completed. In most cases, a clear,homogeneous reaction mixture is formed. The polycondensate can beisolated, for example, by pouring the reaction solution into water andfiltering off the residue and washing it with water until it isacid-free. The polycocondensates have the K values specified in thetable. The polycocondensates 2, 3, 4, 7, 8 and 9 containing acrylic acidin copolymerized form allow the signals typical of polyacrylic acid tobe recognized in the H-NMR (200 MHz, D6-dimethyl sulfoxide).

                  TABLE 1                                                         ______________________________________                                                               Molecular                                              Poly-                  weight of  K value                                     cocon-                 the        of the                                      densate                                                                             Polymer          polymers   polycocond.                                 ______________________________________                                        1     Polymaleic acid  1,000      21.9                                        2     Copolymer of 70% acrylic                                                                       70,000     43.3                                              acid and 30% maleic acid                                                3     Polyacrylic acid 1,000      28.5                                        4     Polyacrylic acid 8,000      30.3                                        5     Copolymer of maleic acid                                                                       10,000     25.6                                              and 1,4-butanediol                                                            monovinyl ether                                                               ethoxylate with 8                                                             ethylene oxide units                                                    6     Copolymer of maleic acid                                                                       70,000     38.1                                              and methyl vinyl ether                                                  7     Modified polyacrylate acid                                                                     4,000      24.1                                        8     Polyacrylic acid 50,000     27.6                                        9     Polyacrylic acid 100,000    42.3                                        ______________________________________                                    

The polycocondensates 1 to 9 are suitable, for example, in amounts from5 to 7% by weight in detergents as encrustation inhibitors.

For the application of the polycocondensates in water treatment, theinhibition of calcium carbonate deposits is of prime importance.Examples are: saccharine juice evaporation, cooling circulations, seawater desalinification plants, steam generators, heating circulations,warm water circulations, heat exchangers, turbines and pumps.

Calcium carbonate inhibition (2 ppm polycocondensate concentration)

2 test solutions are prepared. Test solution 1 consists of water havinga calcium hardness of 20° dH and magnesium hardness of 10° dH. Testsolution 2 is an aqueous solution having a sodium carbonate hardness of4.7° dH and sodium hydrogen carbonate hardness of 12.3° dH.

150 ml of test solution 1 and 150 ml of test solution 2, and 2 ppm ofthe polymer to be tested are initially introduced into a round-bottomedflask of 500 ml capacity which is equipped with a stirrer, refluxcondenser and gas inlet tube and heated at 70° C. for 1 hour whilepassing in air (3 l/h). The contents of the flask are allowed to cooland are filtered through a fluted filter. The calcium content in thefiltrate is determined by complexometric titration according to acustomary method.

The results obtained in this case are indicated in Table 2. The valuesfor the calcium ion tolerability of the polycocondensates 2 to 9 areadditionally listed therein. They show stable solubility even in thepresence of high calcium ion concentrations and can easily prevent theprecipitation of calcium carbonate.

                  TABLE 2                                                         ______________________________________                                        Test for calcium carbonate inhibition:                                                                   Ca ion                                                                        tolerability                                                                  1,000 ppm Ca.sup.2+                                               CaCO.sub.3 inhi-                                                                          45 ppm poly-                                       Polycocon-     bition [%]  cocondensate                                       Example densate    1 h     2 h   [% transmission ]                            ______________________________________                                        10      2          53      50    100                                          11      3          54      50    100                                          12      4          60      61    100                                          13      5          59      57    100                                          14      6          49      39    89.7                                         15      7          70      66    100                                          16      8          64      64    100                                          17      9          50      50    100                                          ______________________________________                                    

The test for clay dispersion offers an assessment of polymers based ontheir use in detergents.

CD test (clay dispersion)

Finely ground china clay SPS 151 is used as a model of particulate dirt.1 g of clay is intensively dispersed in 98 ml of water for 10 minutes ina glass jar (100 ml) with addition of a 0.1% strength sodium saltsolution of the polyelectrolyte. Immediately after the stirring, asample of 2.5 ml is taken from the center of the glass jar and theturbidity of the dispersion is determined using a turbidimeter afterdilution to 25 ml. After a 30- or 60-minute standing time of thedispersion, samples are again taken and the turbidity determined asabove. The turbidity of the dispersion is stated in NTU (nephelometricturbidity units). The less the dispersion settles during storage, thehigher the measured turbidity values and the more stable the dispersion.The second physical measurement determined is the dispersion constant,which describes the temporal behavior of the sedimentation process. Asthe sedimentation process can be described approximately by amonoexponential time law, the dispersion constant τ indicates the timeat which the turbidity falls to 1/e of the starting state at time t=0.

The higher a value for τ, the slower the dispersion settles. The valuesdetermined for some polycocondensates are compiled in Table 3.

                  TABLE 3                                                         ______________________________________                                                     Turbidity in NTU                                                                            Dispersion                                                Polycocon-                                                                            t = 0   t = 30  t = 60                                                                              constant τ                           Example  densate   [min]           [min]                                      ______________________________________                                        18       2         740     610   570   288.5                                  19       3         750     650   580   477.5                                  20       4         760     590   580   854.2                                  21       7         740     600   580   484.4                                  22       8         750     610   570   282.1                                  23       9         750     610   580   352.4                                  Comparison                                                                             Polyacrylic                                                                             770     670   630   345.1                                  example  acid                                                                          M = 8000                                                             ______________________________________                                    

Polycondensates according to the invention are easily able to dispersesolid particles and show the same action as a commercially availablepolyacrylic acid.

We claim:
 1. A polycocondensate based on aspartic acid, consistingessentially of a polycondensate obtained by condensing(a) aspartic acidin the presence of (b) polymers containing carboxyl groups, whichcontain at least 10 mol % of a monoethylenically unsaturated carboxylicacid in copolymerized form and have a molecular weight of at least 300,in the weight ratio (a):(b) from 1,000:1 to 2:1.
 2. A process forpreparing polycocondensates based on aspartic acid, which consistsessentially of condensing (a) aspartic acid or polyaspartic acid in thepresence of (b) polymers containing carboxyl groups, which contain atleast 10 mol % of a monoethylenically unsaturated carboxylic acid incopolymerized form and have a molecular weight of at least 300, orcopolymers containing maleic anhydride groups in the weight ratio(a):(b) from 1,000:1 to 2:1.
 3. A process as claimed in claim 2, whereinthe polymers containing carboxyl groups employed are homopolymers ofmaleic acid or of acrylic acid or copolymers of acrylic acid and maleicacid, the molecular weight of the polymers being from 300 to 250,000. 4.Detergents or cleaners comprising as an additive a polycocondensate asclaimed in claim 1 in the form of the free acid groups or in a formneutralized with ammonia, amines, alkali metal or alkaline earth metalbases.
 5. Scale inhibitors or dispersants for finely divided solidscomprising as an additive a polycondensate as claimed in claim 1 in theform of the free acid groups or in a form neutralized with ammonia,amines, alkali metal or alkaline earth metal bases.